Simulation study investigating the novel use of drive torque vectoring for dynamic post-impact vehicle control

The work presented here investigates the use of drive torque vectoring as a method of post-impact vehicle control. Crash statistics show a high number of serious injuries occurring on British roads, with 46% of the 1713 fatalities in 2013 being car occupants. In total there were 21657 serious injuries sustained across all road users in the same time period. Research has highlighted that people involved in multiple impact crashes have an increased risk of sustaining serious injury compared to those involved in a single impact event (Transport 2013). This highlights post-impact control, as a means to avoid secondary impacts, as an important area of study, an area that is still in its infancy. Work carried out so far that aims to control a vehicle after impact makes use of the braking and/or steering systems. This work has produced reasonable levels of success, however the use of drive torque vectoring control has received little attention. To this end, a non-linear 8 Degree of Freedom model is developed that is capable of simulating a vehicle’s behaviour and trajectory during a crash instigated by an impulse disturbance. These crash impulse disturbances are calculated using momentum theory, taking into account energy loss during the impact. They are used to simulate two vehicle crash scenarios: a rear impact, and a side swipe impact. Simulation of these crash scenarios is carried out on the vehicle model before drive torque vectoring control is implemented to produce a benchmark set of results against which the controlled system is evaluated. The control system presented is a six-phase switched PID controller scheme using a set of ‘Settling’ and ‘Holding’ controllers. The control objective is to settle the vehicle at a heading angle that is parallel to the original (e.g. 00, 1800 or 3600), such that the final trajectory re-aligns the main crash structures of the vehicle with the carriageway so as not to expose the side of the vehicle to a secondary collision. Re-aligning the vehicle with the carriageway before it has come to a stop has the additional benefit of reducing lateral displacement when compared with the benchmark results. This control action results in a reduced risk of a secondary impact and thus of serious injury. This system resulted in safe heading angles for all simulations compared with the current work in the field, leading to safer outcomes for occupants